(ns salesman.core
  "finds the quickest path through cities"
  (:use [clojure.math.combinatorics :only [permutations]]
        [clojure.math.numeric-tower :only [sqrt]]))

(defn random-city []
  {:x (int (rand 10)) :y (int (rand 10))})

(defn random-world [num-cities]
  (take num-cities (repeatedly random-city)))

(defn distance [city-one city-two]
  (let [square (fn [x] (* x x))]
    (sqrt (+ (square (- (:x city-one) (:x city-two))) (square (- (:y city-one) (:y city-two)))))))

(defn total-distance [route]
  (let [distance (reduce + (map #(apply distance %) (partition 2 1 route)))]
    {:distance distance :route route}))

(defn brute-force [list-of-cities]
  (let [routes (map total-distance (permutations list-of-cities))]
    (apply max-key :distance routes)))